Known apparatus for dispensing powdered material such as insecticides or fungicides possess a number of disadvantages both in construction and operation which tend to make their use difficult or complex and their operation inefficient. For example, one class of such apparatus is operated by hand power and these not only tend to be somewhat heavy and clumsy to operate, but also the distribution of the material is non-uniform, depending as it does on the speed and uniformity with which the user operates the equipment. As to the powered apparatus which are also portable, these have in the past involved the carrying of relatively heavy power packs, making them undesirable for certain types of use.
In all of the known equipment, whether hand operated or powered, a recurring problem is that of bridging of the powdered material in the container or hopper. That is, depending upon the cohesive characteristics of the material, an air pocket tends to develop in the hopper in the region adjacent the exit point therefrom, at which time the apparatus dispenses air with very little of the powdered material suspended therein. Then, upon subsequent collapse of the material surrounding the air pocket, the density of suspended material in the emitted air will be suddenly increased beyond what may be the desired amount for which the apparatus was designed. In the matter of dispensing insecticides and fungicides, this changing rate of dispensing is undesirable for the further reason that the materials are frequently poisonous and it is desirable to only dispense to the plants the required amount and no excess, since the plant in some cases can be harmed by excessive amounts of the material. Also, when the materials used are toxic, it is desirable to maintain a uniform and properly mixed amount to reduce exposure to the user of the equipment.